Electrical control apparatus for stokers and the like



April 9, 1940. E. E. POTTER :1- AL ELECTRICAL CONTROL APPARATUS FOR STOKERS AND THE LIKE Filed April 18, 1938 2 Sheets-Sheet 1 INVENTORS.

[155W 1. POITEK.

April 9, 1940. E. E. POTTER ET AL 2,196,802

ELECTRICAL CONTROL APPARATUS FOR STOKERS AND THE LIKE 4 Filed April 18, 1938 2 Sheets-Sheet 2 INSULATION- ATTORNEYJ- Patented Apr. 9, 1940 UNITED STATES.

PATENT OFFICE ELECTRICAL CONTROL APPARATUS FOR STOKERS AND THE LIKE Elbert E. Potter, Princeton, and Richard M. Brumfield, Owensville, Ind., assignors to Potter and Brumfleld Manufacturing (30.,

ing specification and'claim and illustrated in the accompanying drawings.

Fig. 1 is a side elevational view of a time controlled switching unit which forms an important part of the invention. Figs. 2, 3, 4 and 5 are elevational views in section taken on the correspondare perspective views of individual parts of the switch unit shown in Fig. 1. Fig. 10 is a partially diagrammatical view of a stoker installation to which the invention may be applied. Fig. 11 is a 20 diagram of wiring connections by means of which the invention may be applied.

The principal switching unit for use with the invention is shown in Fig. 1. The framework thereof consists of three plates 20, 2| and 22 secured together by spacers 23 and 24 and suitable screw fastenings. To the plate 20, there is attached a casing 25 enclosing a clock mechanism of any desired type, the details of which are not pertinent to the present invention. Said clock is preferably electrically operated but may be of the spring type if desired. A pinion 26 is driven at a uniform speed by the clock and meshes with a gear 21 mounted upon a shaft 28 journaled in the plates 20 and 2|. The shaft 26 carries a pin- 35 ion 29 meshing with a gear 30 freely mounted on a central shaft 3| which is journaled in the plates 2| and 22. Said gear carries a pawl 32 normally retained in engagement with a gear 33 by means of a spring 34. The gear 33 is securedto the shaft 40 3|. The gears 21 and 30 are driven by the clock in the direction of the arrows in Fig. 2 and thus permit the clock to rotate the shaft 3| through the pawl'32. Said shaftmay be turned by hand however in the same direction by means of a knob 35 45 since the pawl 32 will then slip past the teeth of gear 33. i I

A pinion 36 meshes with the gear' 21 and is mounted on a shaft 31 journaled on the plates 20 and 22. Said shaft carries a disc 38 visible 5 through an opening 39 in the plate 22. Said disc indicates by its movement that the clock mechanism is in operation.

On the inner surface of the plate 2| there is placed an insulation member 46, (Figs. 3 and 6). 6 Said member is held in a stationary position by ingly indicated lines of Fig. 1. Figs. 6, 7, 8 and 9' shaft 3| which passes through a central opening 4| therein and by a block 42 of insulation material which hasa tenon 43 (Fig. 9) engaging an opening 44 in the member 4|] and engaging a suitable mortise in the plate 2|. The opposite end of 5 the block 42 has a similar tenon 45 engaging a mortise in the plate 22 and is thus held securely in position. I

Engaging the inner surface of the insulation member 40 there is an electrical contact member 46 (Figs. 3 and '7), which has a central opening 41 surrounding the shaft 3| and sufficiently large to prevent electrical contact therewith. Said member is secured in position by the tenon 43 passing through a mortise 48 therein and is provided with a terminal 43 for the connection of a conductor 50.

A contact member 5| (Fig. 8) engages the contact member 46 and is secured to the surface of a gear 52 formed of insulating material and freely mounted on the shaft 3|. Said contact member has a central opening 53 sufliciently large to prevent electrical contact with the shaft 3| and is. provided with a finger 54 extending around the edge of the gear 52 and adapted to engage the surface of a pair of segmental contact members 55. The contact members 55 are mounted upon an insulating member 56 secured to the shaft 3| and rotatable thereby in the direction of the arrow in Fig. 3. A finger 51 likewise engages the contact segments 55 and is mounted upon the insulation block 42 and is provided with a suitable terminal for the connection of a conductor 58. A gear'59 meshes with the gear 52 and is mounted on a shaft 60, journaled on plates 2| and 22 A knob 6| is carried by the shaft 60 and is man'- u'ally movable to rotate the gear 52 and thus change the position of the finger 54 with relation to the contact segments 55.

It will be noted that the segments 55 are eccentrically mounted and each has a lip 62 extending substantially to the edge of the other, but out of electrical contact therewith. The fingers 54 and 51 are formed of resilient material and are sufliciently fiexed to move quickly from the lip of one segment to the other segment when said lip passes the ends of the fingers. In the position of the parts shown in Fig. 3, the finger 51 engages one'of the contact segments 55 and the finger 54 engages the other. In this position, no electrical connection is established between'said fingers and between the conductors 50 and 58 connected thereto. When shaft 3| has been rotated sufficiently for finger 51 to shift to the same contact segment as finger 54, an electrical consite sides thereof.

nection is established between conductors 58 and 58. This connection endures until shaft 3| is rotated sufiiciently for finger 54 to move from one segment to the other. Since there are two of the segments 55, the connection is established twice during each revolution of shaft 3|.

The fingers 54 and 51 and the segments 55 constitute an electric switch which is periodically operated by rotation of the shaft 3| with a frequency of twice the frequency of rotation of the shaft. The duration of the periods during which the switch is closed may be varied by changing the position of finger 54 by means of the knob 6|. The gear 59 is provided with a blank portion 63 which limits the movement thereof and limits the range of adjustment of said finger. Because of the eccentricity of the contact segments and the provision of the lips 62, the movement of the fingers from one segment to the other is accomplished by a snap action which reduces arcing to a minimum and permits extremely accurate timing.

Resting against the inner surface of the plate 22 there is an insulation member 64 similar in shape to the member 40 (Fig. 6) and held in position by the shaft 3| and the tenon 45 on the insulation block 42. Engaging the insulation member 64 there is a contact member 65 similar in shape to the contact member 46 (Fig. 7) and having a terminal portion 66 to which a conductor 61 may be connected. A contact member 68 similar in form to the contact member 5| (Fig. 8) engages the contact member 65 and is secured to the face of a gear 69 formed of insulating material and freely mounted on the shaft 3|. The gear 69 may be rotated by means of a gear Ill meshing therewith and mounted on a shaft Said shaft is provided with a knob 12 for manual adjustment and the gear 10 is provided with a blank portion 13 which limits the range of said adjustment. The contact-member 68 isprovided with a spring finger 14 adapted to engage a plurality of eccentrically mounted contact segments 15. Said segments are carried by an insulation member 16 secured to the shaft 3| and are rotatable thereby in the direction of the arrows in Figs. 4 and 5. In said figures, the contact segments 15 are shown as four in number, opposite segments being connected electrically by conducting members TI and 18 on oppo- Thus, each opposing pair of segments may be considered as constituting a single contact member. A spring finger 19 formed integrally with the finger 51 also engages the segments 15.

By means of this construction an electrical connection is completed between the fingers I4 and 19 and between the conductors 61 and 58 connected thereto when the fingers I4 and 19 engage opposite segments 15. Said connection is broken when said fingers engage adjacent segments as shown in Figs. 4 and 5. The connection is normally completed each time finger 19 slips from one contact segment to the next and is broken when finger 14 does likewise. Said fingers and contact segments, therefore, comprise an electric switch periodically operated by rotation of the shaft 3| with a frequency four times'the frequency of rotation of said shaft. The duration of the periods during which the switch is closed may be varied by varying the postion of the finger 14 by means of the knob 12. The positions of the contact segments 55 and 15 with relation to each other are such that the closed periods of the 54555'| switch begin substantially simultaneously with certain of the closed periods of the |4|5-'|9 switch.

Secured to the shaft 3| there is a cam 88 having a portion 8| of greater radius than the remainder thereof. Said cam is adapted to engage a humped portion 82 of a contact leaf 83 which is secured to the underside of the insulation block 42 and provided with a terminal to which the conductor 50 is connected. The contact leaf 83 carries a contact point 84 adapted to engage a similar point 85 carried by a contact leaf 86 which is secured beneath the leaf 83 and suitably insulated therefrom. Said leaf is provided with a terminal to which a conductor 81 may be attached. A finger 88 of insulating material is mounted on a shaft 89 journaled on the plates 2| and 22 and provided with a knob 98. Said finger, in the position shown in Fig. 4, engages the leaf 83 and maintains the points 84 and 85 in contact. The shaft 89 also carries an arm 9| having a pin 92 operating in an arcuate slot 93 in the plate 22. An overcenter spring 94 engages said pin and is secured to one of the spacers 24 and serves to maintain said pin in whichever end of the opening 93 it may be set. When said pin is moved by the knob to the opposite end of the opening 93, the finger 88 is moved to the left in Fig.

4 and permits separation of the points 84' and 85. With the parts in that position, the cam 8| may engage the humped portion of the leaf 83 to press said points together. The cam is so shaped that this occurs once in each revolution of the shaft 3| and occurs during the time that the fingers 54 and 51 are both in engagement with one of the contact segments 55. However, when said fingers engage the other of said contact segments, the cam 8| will be out of engagement with the leaf 83 and the points 84 and 85 will be separated. The leaves 83 and 86 and their associated contact points thus constitute an electric switch which may be periodically operated by the rotation of the shaft 3| with a frequency equal to the frequency of rotation of said shaft. The closed period of said switch coincides at least in part with one of the closed periods of the switch 54-555|. By manual operation of the knob 98, however, the switch 83-86 may be set in the'closed position irrespective of the position of shaft 3|.

In Fig. 10 there is shown a furnace 95, a fuel hopper 96, a fuel conduit 91 and a motor 98, included in a common form of stoker installation in which fuel is fed from the hopper 96 through conduit 91 to the retort of the furnace by means of a screw or other conveying means whenever motor 98 is operated. There is also shown a blower 99 adapted to supply air for combustion to the furnace through a conduit I80. Said blower is driven by a motor "H. A preferred form of wiring for the control of the motors 98 and NH is shown in Fig. 11 in which there is included the high frequency switch 14-|5-19, the intermediate frequency switch 54-55-5| and the low frequency switch 83-46 previously described as a part of the switching unit of Fig. 1. There is also included in Fig. 11 a thermostatic switch KIM adapted to close its circuit when the temperature affecting the associated thermostat is below a predetermined degree and to open its circuit when said temperature is above said de gree. Said switch may be of any suitable commercial type. A-motor operating relay I03 when energized supplies power from a pair of power mains I84 to operate the motors 98 and IM. A transformer I05 which may be connected to any suitable source of alternating current such as mains I08 supplies current at a suitable low voltage for the operation of the control circuits for the relay III. The first of said control circuits includes a conductor I01, connected to the transformer secondary, the thermostatic switch I02, conductor 81, the high frequency switch llll-19, conductor 5., relay I03 and a conductor I" connected to the opposite terminal of the transformer secondary. The second control circuit includes conductor 81 connected to the transformer secondary, the low frequency switch 83- 81, conductor 50, the intermediate frequency switch il-It-U, conductor'il, relay I" and conductor llll.

In the operation of the invention the thermostatic switch is operated in the usual manner in response to the temperature of one of the rooms to be heated. When said temperature indicates ahead for heat, said switch is closed and the first control circuit is periodically completed by the operation of the high frequency switch 14-45-19. The completion of the circuit energizes relay I03 which in turn completes the circuits to motors and "II to supply fuel and draft to the furnace. The frequency of the fuel and draft periods then depends upon the frequency of operation of the high frequency switch and'the duration thereof depends upon the ad iustment of finger 14.

When the thermostatic switch shows no need for heat, the second control circuit is completed periodically to operate relay I03 and motors 98 and llll with suflicient frequency to maintain a fire in the furnace. The required frequency and 'duration of such operations depends upon the nature of the fuel, the design of the furnace and the ratio of the rates of supply of fuel and air. For that reason the apparatus provides a choice of two frequencies together with a single adjustment which controls the duration at either frequency. When the lower frequency is required, the knob 90 is operated to move arm 8| to the left in Fig. 4, leaving the low frequency switch "-86 free for time controlled operation by the cam 8|. Since said switch is then closed only during alternate closure periods of the intermediate frequency switch UHF", the second control circuit is completed only once per revolution of shaft 3|. The duration of the closure period of the low frequency switch is preferably greater than the greatest duration of the closed period of the intermediate frequency switch. Therefore, the duration of eachfeedlng period depends only upon the adjustment of the intermediate frequency switch by its knob 8|.

' When the higher frequency of the two is required for the hold fire operation, knob 90 isset to move arm 88 to the position shown in Fig. 4, thus closing the low frequency switch 83-86 and rendering the same inefi'ective to control the frequency of fuel feed. The feeding periods then occur at the intermediate frequency and the duration of said periods again depends only on the setting of the knob 6|.

Preferably the switching unit of Fig. 1 is en closed in a suitable casing (not shown) from which the shafts carrying knobs 35, GI, 12 and 90 protrude. Suitable index marks on the knobs and calibration marks on the casing may be provided to indicate the settings of the several adjustments.

From the foregoing specification it will be apparent that the invention provides means whereby the duration of fuel feeding periods may be accurately controlled within wide limits by simple and convenient manipulation. Likewise, there is provided a readily operable means for choosing the frequency of the hold fire operations with a single means of controlling the duration thereof independent of the frequency.

The details of the invention may be varied within wide limits by those skilled in the art without departing from thescope thereof as defined by the appended claim.

The invention claimed is:

Electrical control apparatus for a stoker having a motor driven fuel feeding mechanism including three time controlled switches having high, intermediate and low frequencies of operation with respect to each other, a thermostatic switch, electric circuits associated with the high frequency switch and the thermostatic switch and operating said motor when said thermostatic switch indicates a need for heat to feed fuel during predetermined periods occurring with the frequency of operation of said high frequency switch, electric circuits associated with the intermediate and low frequency switches and independent of' the thermostatic switch and normally operating said motor to feed fuel during hold fire periods theduration of which is controlled by the intermediate frequency swltch and the frequency of which is controlled by the low frequency switch, manually operated means for adjusting the intermediate frequency switch to vary said duration and manually operated means for rendering said low frequency switch ineffective to-control said circuit whereby the frequency of said periods is controlled by the intermediate frequency swi EIBERT E. POTTER.

RICHARD M. BRULIF'IEID. 

